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How to Fix Dex-Cool Problems on a 1966 Impala SS–Plus More Tech Tips

Techin’ in with Fletch

Dan Fletcher Feb 6, 2015
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Impala Chunks

My problem is with my 1996 Impala SS. What I thought to be a simple heater problem has become much more serious. The problem is Dex-Cool. After back-flushing the heater core I found slimy chunks of clay-like crud throughout. I can only figure that what’s in the heater core is also in the radiator and engine block. The back-flush and coolant change (Dex-Cool) did not help the heater problem. After 20 minutes, the heater once again stopped blowing hot. Is there any product or procedure that can break down the slimy chunks of old Dex-Cool in the system and restore the cooling system and heater core? I have considered an inline filter, but no one makes a coolant filter. Yes, I’m that desperate.

Jim Erskine,
Vacaville, CA.

Once again, a seemingly random type question turns into an educational opportunity for not only the reader but the writer as well. As I researched your question, a proverbial light bulb went on above my head. I’ve had the same problem on a previous occasion myself. Living in beautiful upstate New York, many of us have winter cars so as to preserve the nicer summer cars. The winter POS eventually rots away to nothing, so you wind up replacing it every few winters. A few years ago, I picked up a ’95 4WD Blazer to perform the task, and for the most part, it performed admirably. It did have a heat issue at one point, and I also back-flushed the heater core as one of the steps of repair. The amount of garbage that came out was amazing, but it also didn’t fix the problem for an extended period of time. When we finally replaced the heater core, we just had to cut it open to look. OMG, I should have taken a picture, as it was still so full of trash I couldn’t believe it.

Now that I’ve researched the topic, it’s obvious that tons of people have had a bad Dex-Cool experience. There are all kinds of opinions on how to effectively flush the system, and unfortunately some include hot-tanking the block. I spoke with my friend and general repair mechanic Paul Webber for some insight, and he confirmed that it can be a real pain to eradicate the chunky bits. I’m afraid one system flush might not be enough, and you might not ever get all the junk out of the cracks and crevices of the block.

I’d recommend a high-quality chemical power flush, and you’ll very likely have to perform it on multiple occasions over a period of time. Many folks talk of using dishwashing detergent or the like, but I’d probably stick with a product on the shelves at a local parts retailer. I eventually wound up replacing the heater core to fix my heating issue (and I honestly think you’re going to have to as well), but my POS also got a radiator and all of the hoses during the course of its tenure. As it was a winter bomb, I didn’t really care what the coolant looked like, just that it stayed in the system and that the truck had heat! When it comes time to refill the coolant, may I humbly suggest Peak Long Life or Global Lifetime? Both are exceedingly fine products, and the continued sales of such will help to keep my pathetic little drag racing efforts on track!

Are Zee Brakes Wrong?

I recently bought a 1991 Z28. The previous owner said it was a 350. I checked the VIN to see if the eighth digit was an 8 and it was. I love third-generation Camaros, and I have some information from frequenting the website thirdgen.org. I read on that website that all of the 1991 Z28 350s came with the G92 package, which included disc brakes. In the trunk it shows one of the codes as G92. I was looking at mine recently and saw that it had drum brakes. What’s the deal? Am I mistaken in regards that all ’91 350s came with disc brakes? I believe it was an option on 305s and convertibles. Anyway, I was wondering if you could clear that up for me.

David Eikins
Kansas City, MO

A lot of this sort of stuff can get pretty dicey, and I’d sure hate to give you bad intel. I’ve researched your question thoroughly, and the following is my concerted opinion with the information I’ve obtained. You are correct, the eighth digit of the VIN speaks to the engine combination, and the number 8 dictates that your car was in fact a 350 build. It could be either the B2L or the L98, but in your particular case it appears that you have the B2L 350 with the four-speed automatic transmission. I disagree, however, that all ’91 Z28s with 350s came with the RPO G92, and therefore four-wheel disc brakes.

It’s my understanding that RPO code 1FP87 (Camaro Z28, V8) was produced in a quantity of 12,452. RPO G92 (rear axle performance), which was only available on the Z28, was numbered at 6,813. The following information regarding the RPO G92 is per the camaorsource.ca website.

RPO G92 required one of two engine combinations, the 305ci LB9 V-8 with five-speed manual or the 350ci B2L V-8 with four-speed automatic transmission. When ordered with air conditioning, RPO G92 ($466) included engine oil cooler, four-wheel disc brakes (except for a brief period when four-wheel discs were deleted with a $287 credit), and dual-converter exhaust. When ordered without air conditioning, RPO G92 ($675) added heavy-duty front brakes, aluminum driveshaft and spare wheel, special shocks and fuel pickup, and gas tank baffle. Fog lamps were deleted for weight savings and improved cooling.

As you have located the service parts identification label in the trunk, which is the proper location, and it states G92, it appears to me there are only two possible answers to your query. One is that your car happened to be built during the brief period referenced in the text above. The second is that someone took the disc brakes off and replaced them with the drums you currently have installed. I’m going to have to go with the former.


My wife and I own a 1968 Camaro convertible. It’s a survivor that is still sporting the original 327 and Powerglide transmission with the console shifter. I was thinking about swapping out the Powerglide for a 700-R4 in order to achieve better highway use. I’m just wondering what’s going to be involved (driveshaft length, transmission mount, shifter, etc.), or is there another transmission alternative?

Bob Bucks
Via email

While there are clearly other choices, it’s my opinion that for an application like yours, the 700-R4 is the perfect choice. Not only will you enjoy the 0.70 overdrive on the freeway, but you’ll get the added benefit of the 3.06 low gear to help smoke the tires at the hit. And it’s a very simple swap with a totally proven road map to follow.

As you referenced, there are some changes that will be required, but none are earth shattering by any means. The driveshaft will need to be shortened (yolk can stay as splines are the same), the crossmember will have to be modified or replaced, acquire a dipstick tube and stick, and I definitely think you’d want to change out the shifter. Additionally, you’re going to need to install a TV cable, do something to facilitate control of the lockup converter, and retrofit the speedo if you don’t want to just drive by the tach. Again, no real show-stoppers. A company called Bowtie Overdrives has the whole project lined out, and you check out their website here: bowtieoverdrives.com/index.shtml.

Gear Ratio Rationing

I am planning on buying a 1972 Chevrolet Chevelle. The engine is a 454-cubic-inch displacement. My question is regarding that the car has a 2.73 rear. I am not that familiar with rearend gearing. Given the 454 engine, shouldn’t the car have a higher gear rearend, something more like a 3.73, for example? I really don’t know if I would have any problems with street driving and an occasional expressway drive. Your suggestions would be greatly appreciated.

Harry Gilbert,
Cincinnati, OH

The proper gear ratio for any given car really depends on a number of things. Obviously, a high-winding 302 would generally want more rear gear than a low-compression, somewhat lumbering 454. Secondly, and to me most importantly, what is the specific application? By the tone of your question, I’m guessing that you’re buying this as a total cruiser. If we discuss things in terms of a 60-mph freeway drive, the 2.73 gear will yield just a shade under 2,000 rpm with a 28-inch tall rear tire. If you chose to move to a 3.73, for example, the same speed will cause that mileage wizard of a 454 to spin at almost 2,700 rpm, ergo straight-line performance will improve, but cockpit noise will be higher and your fuel economy will decrease. Here is a neat link to a gear vs. tire height vs. rpm chart on the Summit Racing website that shows you the end result of various combinations: summitracing.com/expertadviceandnews/chartsandguides/rpm-vs-gear-ratio-and-tire-height.

If the Chevelle that you’re looking at has an original configuration ’72 454, it’s still going to make a decent amount of low-end torque and horsepower, but I certainly don’t see the needle of the tachometer moving an excessive amount with regards to clockwise rotation. So, with that in mind, I’d recommend staying with the 2.73 rear gear and go enjoy some ice cream!

Got a restoration question that’s been puzzling you?
Send it to: [ m ] Super Chevy, Fletch, 1733 Alton Pkwy, Suite 100, Irvine, CA 92606. [ e ] questions4fletch@yahoo.com



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